The elements of optics: designed for the use of students in the university / By James Wood.

  • James Wood
Date:
1818
Catalogue details

Licence: Public Domain Mark

Credit: The elements of optics: designed for the use of students in the university / By James Wood. Source: Wellcome Collection.

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    surface RS at the point C; and let CB be the reflected ray; draw CP perpendicular to the reflector. Then, if the plane surface of a board TS be made to coincide with CA and CP, the reflected ray CB is found also to coincide with the plane TS; or the angles of inci¬ dence and reflection are in the same plane. Again, if from C as a center, with any radius CA, the circle RPS be described, the arc AP is found to be equal to the arc PB; therefore the angle of incidence, ACP, is equal to the angle of reflection, BCP. The angles of incidence and reflection are also found to be equal, and in the same plane, when rays are re¬ flected at a curve surface. (19.) Cor. 1. The angles ACR, BCS, which are the complements of the angles of incidence and re¬ flection, are also equal. (20.) Cor. 2. If BC be the incident ray, CA will be the reflected ray. For, the angle PC A is equal to the angle PCB, and in the same plane; therefore CA is the reflected ray. (21.) Cor. 3. If the ray PC be incident perpen¬ dicularly upon the reflecting surface, it will be reflected in the perpendicular CP. (22.) Cor. 4. If AC be produced to E, the angle BCE, which measures the deviation of the ray AC from it’s original course, is 180° - z ACB ; or 180° — 2 z of incidence. (23.) Cor. 5. A ray of light will be reflected at a curve surface, in the same manner as at a plane which touches the curve at the point of incidence. For, the angle of incidence, and consequently the angle of reflection is the same, whether we suppose the reflection to take place at the curve, or at the plane.
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